It is known that a rotary machine supporting a rotary shaft by a bearing has two driving reactive force receiving parts having different rotary phases, and a pump driving apparatus drives two pumps by the same rotary shaft. For example, JP-A-2008-49743 discloses a pump driving apparatus. According to this pump driving apparatus, suction and discharge ports of two rotary pumps are arranged with respect to a rotary shaft so that a phase difference is to be 180 degrees, and axial thicknesses of the two rotary pumps are made to be different. Accordingly, it is possible to cope with a configuration where fluid consumptions (caliper sizes) are different between a front system and a rear system, such as front and rear piping vehicle.
When the pump driving apparatus, which drives the two rotary pumps having the same discharge amount by the same rotary shaft, is applied to the vehicle in which the fluid consumptions are different between the front system and the rear system, if a motor for pump driving is rotated so as to secure a flow rate necessary for the front system, a brake fluid of an excessive flow rate is supplied to the rear system. In this case, current consumption of the motor is wasted. Therefore, according to the pump driving apparatus of JP-A-2008-49743, the axial thicknesses of the two rotary pumps are made to be different, so that the brake fluid having the flow rates necessary for the respective front and rear systems is to be supplied at the same revolution.